The present invention is directed to an expansion composition. More particularly, the present invention relates to an expansion composition that is capable of forming a gel-like substance when heated, having a volume that fluctuates as a function of the temperature of the expansion composition, and preferably creating its own heat when current flows therethrough. Most particularly, the present invention relates to an expansion composition that includes an expandable electric isolator, an elastomer, and electrical conductor particles dispersed throughout the electric isolator and elastomer.
Conventional shock absorbers, damping apparatuses, temperature sensitive actuators, and the like use waxes to perform various functions. Waxes are known to exhibit suitable damping properties in conventional shock absorbers and suitable flow properties in hydraulic devices. Waxes, however, pose difficulties to manufacturers, when placed within shock absorbers and within hydraulic devices. For example, when shock absorbers are used under severe conditions, such as on a rough terrain, the frictional movement of the shock creates internal heat causing the wax to become fluidized and perhaps flow out of the device.
A similar situation can result in a hydraulic device when the device is subjected to multiple compressions or expansions. In addition to shock absorbers and hydraulic devices, waxes are also used in wax motors that open and close flow valves in thermostats that control coolant fluid flow from an engine to a radiator. During operation of such a thermostat, wax that is held inside the thermostat's motor melts and expands as the engine coolant temperature rises above a pre-determined level. The wax expansion causes movement of a piston that, in turn, opens the flow valve to permit coolant flow from the engine to the radiator.
Waxes are poor electrical conductors and require an external heating source if they are to melt and to expand. Despite their poor electrical conductive properties, waxes are of particular interest for use in thermostat motors because waxes expand over temperature ranges of practical significance and are both plentiful and inexpensive. Therefore, in conventional electronically actuated thermostats, electrical heaters are provided to melt the wax held within the wax motor. The external heaters, however, are often cumbersome and add to the manufacturing costs of the thermostat. What is needed is an expansion composition that is inexpensive to manufacture, whose components are plentiful, that forms a gel-like substance when melted, and that preferably selectively regulates the flow of electricity therethrough causing selective self-heating and self-cooling and thus expansion and contraction of the expansion composition without the need for additional heaters and electrical connections.
According to the present invention an expansion composition for use in an electric thermostatic control valve apparatus is provided. The expansion composition is formed to fluctuate in volumetric size between a pre-determined normal operating volume and a pre-determined expanded volume. The expansion composition comprises about 52 to about 58 percent by weight of an expandable electrical isolator and electrical conductor particles dispersed throughout the isolator. The conductor particles are present in the expansion composition in an amount sufficient to conduct electric current flow through the electrical isolator when the expansion composition has the pre-determined normal operating volume and until the expansion composition has increased in volumetric size to the pre-determined expanded volume where the isolator component has substantially isolated the conductor particles from one another.
According to another embodiment of the present invention, there is provided an expansion composition that is capable of melting to a gel-like consistency when heated and of expanding in volumetric size. The expansion composition comprises about 75 to about 97 percent by weight of an expandable electrical isolator and about 3 to about 25 percent weight elastomer. In preferred embodiments, the expansion composition comprises electrical conductor particles scattered throughout the isolator so that the expansion composition will conduct electrical current therethrough during pre-selected conditions.
According to yet another embodiment of the present invention, there is provided an electrically stimulated actuator apparatus for use in a thermostatic control valve. The apparatus comprises an electrically conductive housing having walls that define a cavity, an expansion composition that is held within the cavity and that selectively conducts electrical current therethrough, and a piston that extends into the cavity and engages the expansion composition. When electrical current is initially applied to the expansion composition, the current passes through the expansion composition causing it to melt and therefore increase in volumetric size. This increase in expansion volume forces the piston out from the cavity. The ability of the expansion composition to conduct electrical current therethrough is a function of the volume of the expansion composition. So, when the expansion volume of the expansion composition has increased to a pre-determined expanded volume pressing the piston to the fully extended position, the expansion composition itself substantially blocks the flow of electric current therethrough. As a result, the temperature of the expansion composition begins to cool and its expansion volume to decrease in volumetric size allowing the piston to move back into the cavity.
Further, in accordance with yet another embodiment of the present invention there is provided a thermostatic control valve apparatus for controlling fluid flow through an engine cooling system. The apparatus includes an electrically conductive stationary valve member that has a valve seat, a moveable valve member, an electrically conductive motor coupled to the movable valve member, and a spring that extends between the stationary valve member and the electrically conductive motor to help bias the movable valve member to a normally closed position against the valve seat. The electrically conductive motor includes an electrically conductive housing that defines a cavity, an electrically conductive piston that extends into the cavity, and a selectively conductive expansion composition held in the cavity in communication with the piston. The expansion composition comprises an expandable electrical isolator and electrical conductor particles dispersed throughout the isolator. The expansion composition's volume is a function of the expansion composition's temperature and it's temperature is a function of the amount of electrical current running therethrough. The ability of the expansion composition to conduct electrical current therethrough is in turn a function of the volume of the expansion composition. Therefore, when the particles conduct electrical current through the expansion composition, the temperature of the isolator component increases causing the expansion composition to melt and therefore increases in volumetric size. The increase in volumetric size forces the piston out from the cavity where it presses the moveable valve member to an open position away from the valve seat. When the volumetric size of the expansion composition has increased to the pre-determined expanded volume, the conductor particles become substantially isolated from one another and are substantially prevented from conducting electric current through the isolator component. As a result, the temperature and thus the volumetric size of the expansion composition begins to decrease. As the expansion volume decreases, the particles again become in electrical communication with one another and thus the expansion composition's ability to conduct electricity increases. So, depending upon the electric signals provided to the ECM from the sensors and the ECM's response to those signals, the expansion composition may either remain heated and keep the piston pressed out from the cavity or be permitted to cool allowing the spring to bias the piston back into the cavity.
The expansion composition of the present invention also serves as a fail-safe mechanism for electrically actuated motors. Should a controller or an electrical connection fail, heated fluid flow through an engine block and past the electrically conductive motor that houses the expansion composition will increase the temperature of the expansion composition causing the expansion composition to melt. As previously discussed, the melted expansion composition expands in volumetric size and forces the piston out from the cavity and thus the movable valve away from the valve seat.
Advantageously, the expansion composition of the present invention enables manufacturers of shock absorbers, hydraulic devices, and electronically actuated thermostats to use an inexpensive and plentiful expansion composition having the benefits of traditional wax without the difficulties associated with liquidation of the melting wax and the added expense of electric heaters and additional wiring. Additionally, in preferred embodiments manufacturers are able to change the fail-safe actuation temperature of a thermostat by simply manipulating the electrical isolator component of the expansion composition.